Figure 4. Role of SRSF1 in promoting exon inclusion.

(A) Alternative splicing of Illumina short-read data was analyzed using rMATS, and genes with alternatively spliced exons were subjected to Gene Ontology (GO) analysis using ClusterProfiler. (B) Sashimi plot depicting significant alternative splicing of KAT5 exon 5 between PRMT5 inhibitor (JNJ-64619178) and DMSO-treated cells based on Illumina short‑read RNA‑seq. (C) Skipped KAT5 exon in JNJ-64619178–treated cells, consistent with KAT5 exon 5 annotation from the UCSC Genome Browser. (D) SRSF1-binding motifs cluster around cassette exons that are skipped after PRMT5 inhibition. Meta-plots were generated with rMAPS2 using a 50-nt sliding window. Solid traces (motif score, left y-axis): blue line, exons whose inclusion decreases after JNJ-64619178 treatment (down-regulated; n = 6,455); red line: exons whose inclusion increases after treatment (up-regulated; n = 2,596); gray line, cassette exons with unchanged inclusion (background; n = 14,256). The solid curves plot the mean SRSF1 motif score at each position. Dotted traces (right y-axis): corresponding −log₁₀ (P-values) from a Wilcoxon rank-sum test comparing motif scores in each regulated set with background. Prominent peaks in the blue profile, accompanied by high −log₁₀ (P-values), reveal significant enrichment of SRSF1-binding motifs both upstream and downstream of exons that become skipped when PRMT5 activity is lost, consistent with diminished SRSF1-dependent exon inclusion under PRMT5 inhibition. (D, E) rMAPS2 meta-plot of SRSF1-motif density flanking introns whose retention changes after PRMT5 inhibition; same axis format as (D).